Serine-threonine Protein Kinase Akt Research Articles

Banxia Xiexin decoction ameliorates dextran sulfate sodium (DSS)-induced ulcerative colitis via inhibiting serine-threonine protein kinase (Akt)/mitogen-activated protein kinase (MAPK) signaling pathway.

Banxia Xiexin decoction (BXD), a traditional Chinese medicine, was widely used in treating ulcerative colitis (UC). However, the active components of BXD and its mechanism in UC remain elusive. Therefore, we used network pharmacology in vivo experiments, molecular docking, and surface plasmon resonance strategy (SPR) to uncover BXD's potential mechanism. A UC rat model was established by orally administering 7% dextran sulfate sodium (DSS) in drinking water, BXD and palmatine were orally administered for 7days. Network pharmacology was used to investigate the main bioactive components and crucial targets of BXD in treating UC. Molecular docking was used to investigate interactions between components and crucial targets, verifying the results by SPR. By network pharmacology predicting, 20 active components and 44 candidate anti-UC targets of BXD were identified, and the crucial proteins were screeded from PPI network, including extracellular regulated protein kinases (ERK), AKT1, and tumor necrosis factor-α (TNF). In addition, some key active components (palmatine, sexangularetin, and skullcapflavone II) were screened out from the active components-targets network. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment and in vivo experiments showed that protein-serine-threonine kinase (Akt)/MAPK pathway was involved in BXD treatment for UC; BXD and palmatine significantly ameliorated the severity of DSS-induced UC in rats. Our study might assist in further investigation of the active components in Chinese medicine.

Neuregulin-1/PI3K signaling effects on oligodendrocyte proliferation, remyelination and behaviors deficit in a male mouse model of ischemic stroke

In this study, we investigated the effect of neuregulin-1 (NRG1) on demyelination and neurological function in an ischemic stroke model, and further explored its neuroprotective mechanisms. Adult male ICR mice underwent photothrombotic ischemia surgery and were injected with NRG1 beginning 30 min after ischemia. Cylinder and grid walking tests were performed to evaluate the forepaw function. In addition, the effect of NRG1 on neuronal damage/death (Cresyl violet, CV), neuronal nuclei (NeuN), nestin, doublecortin (DCX), myelin basic protein (MBP), non-phosphorylated neurofilaments (SMI-32), adenomatous polyposis coli (APC), erythroblastic leukemia viral oncogene homolog (ErbB) 2, 4 and serine-threonine protein kinase (Akt) in cortex were evaluated using immunohistochemistry, immunofluorescence and western blot. The cylinder and grid walking tests exposed that treatment of NRG1 observably regained the forepaw function. NRG1 treatment reduced cerebral infarction, restored forepaw function, promoted proliferation and differentiation of neuron and increased oligodendrogliogenesis. The neuroprotective effect of NRG1 is involved in its activation of PI3K/Akt signaling pathway via ErbB2, as shown by the suppression of the effect of NRG1 by the PI3K inhibitor LY294002. Our results demonstrate that NRG1 is effective in ameliorating the both acute phase neuroprotection and long-term neurological functions via resumption of neuronal proliferation and differentiation and oligodendrogliogenesis in a male mouse model of ischemic stroke.

Efficiency of Biobran/MGN-3, an Arabinoxylan Rice Bran, in Attenuating Diabetes-Induced Cognitive Impairment of the Hippocampus via Oxidative Stress and IR/Akt/NF-κB in Rats.

Type 2 diabetes mellitus (T2DM) is a common metabolic disease accompanied by cognitive impairment, hippocampal malfunctioning, and inflammation. Biobran/MGN-3, an arabinoxylan rice bran, has been shown to have an antidiabetic effect in streptozotocin-induced diabetic rats. The present study investigates Biobran's effect against diabetes-induced cognitive impairment and synaptotoxicity in the hippocampus via oxidative stress and the IR/A/NF-κB signaling pathway in rats. Diabetes was induced via i.p. injection of streptozotocin (STZ) (40 mg/kg BW); STZ-treated rats were then administered Biobran (100 mg/kg BW) for 4 wks. Biobran supplementation improved motor coordination and muscular strength, as assessed by Kondziella's inverted screen test. Biobran also improved concentration levels of glutathione (GSH), antioxidant enzymes, acetylcholine (ACh), dopamine, serotonin, insulin receptor (IR), and alpha serine-threonine protein kinase (Akt); it protected against elevated levels of glucose, total cholesterol, triglycerides, oxidative stress markers, TBARS, NO, AChE, and MAO; and it significantly decreased inflammatory cytokines levels of IL-1β, NF-κB, TNF-α, and amyloid β1-42. Moreover, Biobran ameliorated hippocampal histological alterations. Immunohistochemical observations showed that Biobran reduced overexpression of hippocampal synaptophysin and Ki67 relative to untreated diabetic rats. Biobran may ameliorate hippocampal alterations in diabetic rats via its antidiabetic, antiproliferative, anti-inflammatory, antiapoptotic, and antioxidant effects.

Propionate ameliorates diabetes-induced neurological dysfunction through regulating the PI3K/Akt/eNOS signaling pathway

A large body of research has established diabetes-related cognitive deterioration, sometimes known as “diabetic encephalopathy”. Current evidence supports that oxidative stress, neuronal apoptosis, and cerebral microcirculation weakness are associated with cognition deficits induced by diabetes. The present study explores the effect of propionate on neurological deficits, cerebral blood flow, and oxidative stress in diabetic mice. Propionate in different doses (37.5, 75 and 150 mg/kg) was orally administrated daily. Here, we show that propionate can markedly improve neurological function, which is correlated with its capabilities of stimulating nitrogen monoxide (NO) production, increasing cerebral microcirculation, suppressing oxidative stress, and reducing neuron loss in the hippocampus. In addition, the results of Western Blotting indicated that the brain-protective function of propionate in streptozocin (STZ)-induced type 1 diabetes mellitus (T1DM) mice is related to phosphoinositide 3-kinase (PI3K)/serine-threonine protein kinase (Akt)/endothelial nitrogen monoxide synthase (eNOS) signaling pathway. In a diabetic mouse model, propionate reduces cerebral microcirculation, hippocampus apoptosis, and neurological impairment. Thus, propionate, now employed as a food preservative, may also help slow diabetes-induced cognitive loss.

Mutant Huntingtin Impairs Pancreatic β-cells by Recruiting IRS-2 and Disturbing the PI3K/AKT/FoxO1 Signaling Pathway in Huntington's Disease.

Patients with Huntington's disease (HD) have an increased incidence of diabetes. However, the molecular mechanisms of pancreatic β-cell dysfunction have not been entirely clarified. Revealing the pathogenesis of diabetes can provide a novel understanding of the onset and progression of HD, as well as potential clues for the development of new therapeutics. Here, we demonstrated that the mouse pancreatic insulinoma cell line NIT-1 expressing N-terminal mutant huntingtin (mHTT) containing 160 polyglutamine (160Q cells) displayed lower cell proliferative ability than the cells expressing N-terminal wild-type HTT containing 20 polyglutamine (20Q cells). In addition, 160Q cells were more prone to apoptosis and exhibited deficient glucose-stimulated insulin expression and secretion. Furthermore, insulin signaling molecule insulin receptor substrate 2 (IRS-2) expression decreased and was recruited into mHTT aggregates. Consequently, glucose stimulation failed to activate the downstream molecule phosphatidylinositol-3 kinase (PI3K) in 160Q cells, leading to reduced phosphorylation levels of serine-threonine protein kinase AKT and forkhead box protein O1 (FoxO1). These data indicate that activation of the glucose-stimulated PI3K/AKT/FoxO1 signaling pathway is significantly blocked in pancreatic β-cells in HD. Importantly, insulin treatment inhibited the aggregation of mHTT and significantly improved the activation of PI3K/AKT/FoxO1 signaling in 160Q cells. These results suggest that the inhibition of the PI3K/AKT/FoxO1 pathway might be due to the recruitment of IRS-2 into mHTT aggregates in HD β-cells, ultimately contributing to the impairment of pancreatic β-cells. In conclusion, our work provides new insight into the underlying mechanisms of the high incidence of diabetes and abnormal glucose homeostasis in HD.

6-Gingerol attenuates microglia-mediated neuroinflammation and ischemic brain injuries through Akt-mTOR-STAT3 signaling pathway

Neuroinflammation is critical for the pathogenesis of ischemia brain damage. Over-activated microglia-mediated inflammation plays a very important role in ischemia cerebral injuries. 6-Gingerol, obtained from edible ginger (Zingiber Officinale) exhibits protective effects against inflammation. In this study, we found that 6-Gingerol could reduce the size of infarction (P = 0.0184) and improve neurological functions (P = 0.04) at the third day after ischemic brain injury in vivo. Since 6-Gingerol has the anti-inflammatory effects, we further investigated its impacts on neuroinflammation mediated by microglia both in vivo and in vitro. We found that the levels of pro-inflammatory cytokines Interleukin-1 beta (IL-1β, P = 0.0213), Interleukin-6 (IL-6, P = 0.0316), and inducible NO synthase (iNOS, P = 0.0229) in the infarct penumbra were lower in 6-Gingerol treated groups. Furthermore, microglia induced pro-inflammatory cytokines, such as IL-6, IL-1β, incremental intercellular nitric oxide (NO), as well as iNOS were blocked by the treatment of 6-Gingerol in lipopolysaccharide (LPS) stimulated microglia. In terms of mechanism, 6-Gingerol potently suppressed phosphorylation of serine-threonine protein kinase (Akt) - mammalian target of rapamycin (mTOR) - signal transducer and activator of transcription 3 (STAT3) in LPS-treated microglia. Taken together, the present study suggested that 6-Gingerol improved cerebral ischemia injury by suppressing microglia-mediated neuroinflammation by down-regulating Akt-mTOR-STAT3 pathway.

The PI3k/Akt pathway is associated with angiogenesis, oxidative stress and survival of mesenchymal stem cells in pathophysiologic condition in ischemia.

Ischemic diseases are characterized by reduced blood supply to a tissue or an organ due to obstruction of blood vessels. The most serious and most common ischemic diseases include ischemic heart disease, ischemic stroke, and critical limb ischemia. Revascularization is the first choice of therapy, but the cell therapy is being introduced as a possible way of treatment for no-option patients. One of the possibilities of cell therapy is the use of mesenchymal stem cells (MSCs). MSCs are easily isolated from bone marrow and can be defined as non-hematopoietic multipotent adult stem cells population with a defined capacity for self-renewal and differentiation into cell types of all three germ layers depending on their origin. Since 1974, when Friedenstein and coworkers (Friedenstein et al. 1974) first time isolated and characterized MSCs, MSC-based therapy has been shown to be safe and effective. Nevertheless, many scientists and clinical researchers want to improve the success of MSCs in regenerative therapy. The secret of successful cell therapy may lie, along with the homing, in secretion of biologically active molecules including cytokines, growth factors, and chemokines known as MSCs secretome. One of the intracellular signalling mechanism includes the activity of phosphatidylinositol-3-kinase (phosphoinositide 3-kinase) (PI3K) - protein kinase B (serine-threonine protein kinase Akt) (Akt) pathway. This PI3K/Akt pathway plays key roles in many cell types in regulating cell proliferation, differentiation, apoptosis, and migration. Pre-conditioning of MSCs could improve efficacy of signalling mechanism.

Increased Angiopietin-2 expression, enhanced proliferation, migration and formation of blood vessels in hemangioma-derived stem cells

Objective To investigate the effect of Angiopoietin-2 (Ang2) up-regulation on the biological function of hemangioma stem cells (HemSCs). Methods HemSCs was isolated and purified by enzyme digestion and immunomagnetic beads sorting. HemSCs was stably up-regulated by Ang2 by lentiviral transfection. The expression level of secreted Ang2 and vascular endothelial growth factor (VEGF) in HemSCs up-regulated by Ang2 was detected by enzyme linked immunosorbent assay (ELISA) method. EDU method The Trangswell method was used to observe the proliferation and migration ability of HemSCs cells up-regulated by Ang2. The tumor formation of nude mice was observed by single cell suspension. The tumorigenic ability of HemSCs was up-regulated by Ang2. The expression of key target proteins in phosphatidylinositol 3 kinase (PI3K)/serine-threonine protein kinase (Akt) cell signaling pathway was detected by Western blotting. Results The proliferation of HemSCs cells up-regulated by Ang2 was enhanced (blank group: 117.000±3.786, control group: 126.000±3.464, experimental group: 179.667±2.603, P<0.01), and migration ability was enhanced (blank group: 102.667±2.028, control group: 108.000±2.646, experimental group: 308.667±2.603, P<0.01); Ang2 in HemSCs Ang2↑ group (blank group: 60.103±0.361, control group: 69.343±0.526, experimental group: 1 962.440±43.205, P<0.01), VEGF (The blank group: 92.667±3.480, the control group: 91.000±1.523, the experimental group: 455.000±15.100, P<0.01) the expression of secreted protein was up-regulated; PI3K-Akt signaling pathway-related protein: Akt1 (blank group: 0.612±0.163, control group: 0.624±0.163, experiment Group: 0. 907±0.162, P<0.01), PI3K (blank group: 0.624±0.163, control group: 0.474±0.163, experimental group: 0.766±0.162, P<0.01), PI3KR5 (blank group: 0.505±0.163, control group: 0.405±0.163, Experimental group: 0.890±0.162, P<0.01), PAkt (blank group: 0.549±0.163, control group: 0.644±0.163, experimental group: 0.684±0.162, P<0.01), p38 (blank group: 0.618±0.163, control Group: 0.759±0.163, experimental group: 0. 947±0.162, P<0.01) Enhanced expression in HemSCs Ang2↑ group. Conclusion Upregulation of Ang2 can enhanced HemSCs proliferation, migration, in vivo angiogenesis; through PI3K-Akt signaling pathway Development has an impact. Key words: Hemangioma; Stem cell; Ang-Tie2 lentivirus; Signaling pathway

Effect of microRNA-153 targeting phosphatidylinositol 3 kinase/serine-threonine protein kinase signaling pathway on proliferation in acute lymphoblastic leukemia cell

Objective To investigate the effect of microRNA (miRNA, miR)-153 on the proliferation and apoptosis of in human acute lymphoblastic leukemia (ALL) cell line Jurkat cells by phosphatidylinositol 3 kinase (PI3K)/serine-threonine protein kinase (Akt) pathway. Methods After miR-153 mimics (miR-153 mimics group) and miR-153 inhibitor (miR-153 inhibitor group) were transfected into Jurkat cells, cell proliferation, cycle and apoptosis. was detected; the expression of miR-153, PI3K and Akt mRNA and protein was measured; whether PI3K was the target gene of miR-153. was confirmed. Results Compared with the negative control group, the expression of miR-153 in the miR-153 mimics group was significantly increased by approximately 10-fold (t=39.596, P<0.01), and the expression of miR-153 was significantly decreased in the miR-153 inhibitor group (t=14.651, P<0.01). The activity of the cells in the miR-153 mimics group was significantly decreased (t=10.931, P<0.01), and the activity of the miR-153 inhibitor group was significantly increased (t=7.640, P<0.01). The expression of PI3K total protein, PI3K mRNA and p-Akt in the miR-153 mimics group was significantly decreased (t=7.161, P<0.01; t=6.684, P<0.01; t=10.769, P<0.01), and the expression of PI3K total protein, PI3K mRNA and p-Akt in the miR-153 inhibitor group was significantly increased (t=3.998, P<0.05; t=8.902, P<0.01; t=7.078, P<0.01). The proportion of G0/G1 phase cells increased significantly, while the S phase and G2/M phasecells decreased significantly (t=3.786, P<0.05; t=3.012, P<0.05; t=4.948, P<0.01) in the miR-153 mimics group; the G0/G1 phase cells decreased significantly, and the proportion of cells in S phase and G2/M phase increased significantly (t=5.356, P<0.01; t=3.055, P<0.05; t=3.893, P<0.05) in the miR-153 inhibitor group. The apoptosis rate of the miR-153 mimics group was significantly increased (t=4.673, P<0.05), while the apoptotic rate of the miR-153 inhibitor group was significant decline (t=5.618, P<0.01). Compared to the empty plasmid group, the relative luciferase activity of 3’untranslated regions (3’UTR) plasmid group was significantly reduced (t=7.925, P<0.01). Conclusion MiR-153 can directly target PI3K/Akt signaling pathway and regulate Jurkat cell proliferation and apoptosis. Key words: Acute lymphoblastic leukemia; MicroRNA-153; Phosphatidylinositol 3 kinase/serine-threonine protein kinase signaling pathway

Bacillomycin D-C16 triggers apoptosis of gastric cancer cells through the PI3K/Akt and FoxO3a signaling pathways.

Bacillomycin D can inhibit the growth of Aspergillus ochraceus in food samples. In addition, it can induce apoptosis in and inhibit the proliferation of cancer cells, although the details of this mechanism are unknown. In this study, we separated bacillomycin D-C14, D-C15, D-C16 monomers from the Bacillus subtilis strain fmbJ. The bacillomycin D monomers containing longer fatty acid chains better induced apoptosis in Bgc-823, Sgc-7901, and Hgc-27 gastric cancer cells. The Bgc-823 cell line was the most sensitive. Acridine orange-ethidium bromide staining indicated that bacillomycin D-C16-induced Bgc-823 cell death by triggering apoptosis, characterized by membrane blebbing, cellular shrinkage, and DNA fragmentation. Flow cytometric analysis showed a bacillomycin D-C16 dose-dependent trigger of Bgc-823 apoptosis. Bacillomycin D-C16-induced the mitochondrial pathway, as indicated by a reduced Bcl-2/Bax expression ratio, enhanced cytochrome C release, and higher levels of cleaved caspase-3. Furthermore, bacillomycin D-C16 effectively repressed phosphorylation of the serine-threonine protein kinase Akt at Ser-473 and increased the levels of the FoxO3a protein. The combination of the PI3K/Akt-inhibitor BEZ235 with bacillomycin D-C16 enhanced the apoptosis of Bgc-823 cells. Together, these findings indicated that bacillomycin D-C16 induces apoptosis through the PI3K/Akt and FoxO3a signaling pathways.

Application of insulin signaling to predict insect growth rate in Maruca vitrata (Lepidoptera: Crambidae).

Insect growth is influenced by two major environmental factors: temperature and nutrient. These environmental factors are internally mediated by insulin/insulin-like growth factor signal (IIS) to coordinate tissue or organ growth. Maruca vitrata, a subtropical lepidopteran insect, migrates to different climate regions and feeds on various crops. The objective of this study was to determine molecular tools to predict growth rate of M. vitrata using IIS components. Four genes [insulin receptor (InR), Forkhead Box O (FOXO), Target of Rapamycin (TOR), and serine-threonine protein kinase (Akt)] were used to correlate their expression levels with larval growth rates under different environmental conditions. The functional association of IIS and larval growth was confirmed because RNA interference of these genes significantly decreased larval growth rate and pupal weight. Different rearing temperatures altered expression levels of these four IIS genes and changed their growth rate. Different nutrient conditions also significantly changed larval growth and altered expression levels of IIS components. Different local populations of M. vitrata exhibited significantly different larval growth rates under the same nutrient and temperature conditions along with different expression levels of IIS components. Under a constant temperature (25°C), larval growth rates showed significant correlations with IIS gene expression levels. Subsequent regression formulas of expression levels of four IIS components against larval growth rate were applied to predict growth patterns of M. vitrata larvae reared on different natural hosts and natural local populations reared on the same diet. All four formulas well predicted larval growth rates with some deviations. These results indicate that the IIS expression analysis explains the growth variation at the same temperature due to nutrient and genetic background.

ALK is a therapeutic target for lethal sepsis.

Sepsis, a life-threatening organ dysfunction caused by infection, is a major public health concern with limited therapeutic options. We provide evidence to support a role for anaplastic lymphoma kinase (ALK), a tumor-associated receptor tyrosine kinase, in the regulation of innate immunity during lethal sepsis. The genetic disruption of ALK expression diminishes the stimulator of interferon genes (STING)-mediated host immune response to cyclic dinucleotides in monocytes and macrophages. Mechanistically, ALK directly interacts with epidermal growth factor receptor (EGFR) to trigger serine-threonine protein kinase AKT phosphorylation and activate interferon regulatory factor 3 (IRF3) and nuclear factor κB (NF-κB) signaling pathways, enabling STING-dependent rigorous inflammatory responses. Moreover, pharmacological or genetic inhibition of the ALK-STING pathway confers protection against lethal endotoxemia and sepsis in mice. The ALK pathway is up-regulated in patients with sepsis. These findings uncover a key role for ALK in modulating the inflammatory signaling pathway and shed light on the development of ALK-targeting therapeutics for lethal systemic inflammatory disorders.

Effects of prenatal caffeine exposure on glucose homeostasis of adult offspring rats.

Epidemiological evidences show that prenatal caffeine exposure (PCE) could induce intrauterine growth retardation (IUGR). The IUGR offspring also present glucose intolerance and type 2 diabetes mellitus after maturity. We have previously demonstrated that PCE induced IUGR and increased susceptibility to adult metabolic syndrome in rats. This study aimed to further investigate the effects of PCE on glucose homeostasis in adult offspring rats. Pregnant rats were administered caffeine (120mg/kg/day, intragastrically) from gestational days 11 to 20. PCE offspring presented partial catch-up growth pattern after birth, characterizing by the increased body weight gain rates. Meanwhile, PCE had no significant influences on the basal blood glucose and insulin phenotypes of adult offspring but increased the glucose tolerance, glucose-stimulated insulin section and β cell sensitivity to glucose in female progeny. The insulin sensitivity of both male and female PCE offspring were enhanced accompanied with reduced β cell fraction and mass. Western blotting results revealed that significant augmentation in protein expression of hepatic insulin signaling elements of PCE females, including insulin receptor (INSR), insulin receptor substrate 1 (IRS-1) and the phosphorylation of serine-threonine protein kinase (Akt), was also potentiated. In conclusion, we demonstrated that PCE reduced the pancreatic β mass but increased the glucose tolerance in adult offspring rats, especially for females. The adaptive compensatory enhancement of β cell responsiveness to glucose and elevated insulin sensitivity mainly mediated by upregulated hepatic insulin signaling might coordinately contribute to the increased glucose tolerance.

Molecular pathways of chronic kidney disease progression

Chronic kidney disease is characterized by the progressive loss of functional nephrons. This loss means that the remaining nephrons are put under stress and are forced to adapt in order to maintain kidney function. Over the time, the strains imposed by these adaptations result in a vicious circle in which the loss of damaged nephrons results in the damage of the so far healthy nephrons. Hence, the rate of chronic kidney disease progression depends on the ability of the remaining nephrons to cope with stress. This article reviews the molecular pathways involved in the compensation and deterioration process after nephron reduction. In particular, we examine the role of mammalian target of rapamycin complex (mTORC)/serine-threonine protein kinase AKT, epidermal growth factor receptor (EGFR) and unfolded protein response pathways, as well as the pleiotropic function of Lipocalin 2. We also discuss the dual role played by some of these pathways in acute and chronic kidney disease. Finally, the relevance of these experimental finding to human chronic kidney disease is discussed.

Seapolynol and Dieckol Improve Insulin Sensitivity through the Regulation of the PI3K Pathway in C57BL/KsJ-db/db Mice

<i>Ecklonia cava</i>, a brown alga native to the seas of Korea and Japan, contains biologically active polyphenols. Seapolynol (SN) is a polyphenol mixture derived from <i>Ecklonia cava</i>, and dieckol (DK) is a major compound of SN. Both <i>Ecklonia cava</i>-derived polyphenols exert an anti-diabetic effect in C57BL/KsJ-db/db mice. SN and DK supplementation significantly reduced bodyweight, water intake, fasting blood glucose, and plasma insulin levels compared with db/db mice. In addition, C-peptide, a biomarker of insulin secretion, was significantly decreased by SN and DK treatment, whereas plasma adiponectin levels, which are associated with insulin sensitivity, was increased by two-fold compared with the db/db group. Regarding plasma lipid profiles, triacylglycerol, total cholesterol, and low-density lipoprotein (LDL) cholesterol, were effectively reduced in the SN- and DK-treated groups. Moreover, the administration of SN and DK activated the insulin signaling pathway, as indicated by the levels of receptor substrate-1 (IRS-1), phosphoinositide 3-kinase (PI3K), serine-threonine specific protein kinase (Akt), and glucose transporter type 4 (GLUT4) in diabetic mice. This result showed that SN and DK regulate blood glucose levels by improving insulin sensitivity in the diabetic condition. Our data suggest that SN and DK may be anti-diabetic agents.

The role of mouse Akt2 in insulin-dependent suppression of adipocyte lipolysis in vivo.

The release of fatty acids from adipocytes, i.e. lipolysis, is maintained under tight control, primarily by the opposing actions of catecholamines and insulin. A widely accepted model is that insulin antagonises catecholamine-dependent lipolysis through phosphorylation and activation of cAMP phosphodiesterase 3B (PDE3B) by the serine-threonine protein kinase Akt (protein kinase B). Recently, this hypothesis has been challenged, as in cultured adipocytes insulin appears, under some conditions, to suppress lipolysis independently of Akt. To address the requirement for Akt2, the predominant isoform expressed in classic insulin target tissues, in the suppression of fatty acid release in vivo, we assessed lipolysis in mice lacking Akt2. In the fed state and following an oral glucose challenge, Akt2 null mice were glucose intolerant and hyperinsulinaemic, but nonetheless exhibited normal serum NEFA and glycerol levels, suggestive of normal suppression of lipolysis. Furthermore, insulin partially inhibited lipolysis in Akt2 null mice during an insulin tolerance test (ITT) and hyperinsulinaemic-euglycaemic clamp, respectively. In support of these in vivo observations, insulin antagonised catecholamine-induced lipolysis in primary brown fat adipocytes from Akt2-deficient mice. These data suggest that suppression of lipolysis by insulin in hyperinsulinaemic states can take place in the absence of Akt2.

Phosphoinositide 3-kinase/Akt Pathway Mediates Fip1-like1-platelet-derived Growth Factor Receptor α-induced Cell Infiltration and Activation: Possible Molecular Mechanism for the Malignant Phenotype of Chronic Eosinophilic Leukemia

The fip1-like1/platelet-derived growth factor receptor-α fusion gene (F/P) is responsible for 14-60% cases of hypereosinophilia syndrome (HES), also known as F/P-positive chronic eosinophilic leukemia (F/P(+) CEL). The major pathogenesis of F/P(+) CEL is known to involve migration and activation of mast cells and eosinophils, leading to severe multi-organ dysfunction, but the mechanism was still unclear. Phosphoinositide 3-kinase (PI3K) and serine-threonine protein kinase Akt have been reported to be targets of F/P in the F/P-promoted cell proliferation. They are extensively involved in the migration and adhesion of hematopoietic stem/progenitor cells, and also control cell invasion in some leukemias. The PI3K/Akt pathway is involved in eosinophil/neutrophil activation and infiltration; its possible role in regulating F/P induced cytotoxicity and upregulation of A4-integrin in eosinophils, and inducing eosinophil activation through controlling F/P-induced Nuclear factor-kB activity. Akt was recently shown to be stimulated by F/P, synergistically with stem cell factor, resulting in the induction of MCs migration and excessive activation. PI3K/Akt pathway is also a principal mediator of interleukin-5 (IL-5)-induced signal transduction promoting eosinophil trafficking and degranulation, whereas IL-5 is a necessary cytokine for F/P-mediated CEL development. We, therefore, propose the hypothesis that the PI3K/Akt pathway might be vital downstream of F/P to induce target cell activation and tissue infiltration, resulting in the malignant phenotype seen in F/P(+) CEL.

Serine-threonine protein kinase activation may be an effective target for reducing neuronal apoptosis after spinal cord injury

The signaling mechanisms underlying ischemia-induced nerve cell apoptosis are poorly understood. We investigated the effects of apoptosis-related signal transduction pathways following ischemic spinal cord injury, including extracellular signal-regulated kinase (ERK), serine-threonine protein kinase (Akt) and c-Jun N-terminal kinase (JNK) signaling pathways. We established a rat model of acute spinal cord injury by inserting a catheter balloon in the left subclavian artery for 25 minutes. Rat models exhibited notable hindlimb dysfunction. Apoptotic cells were abundant in the anterior horn and central canal of the spinal cord. The number of apoptotic neurons was highest 48 hours post injury. The expression of phosphorylated Akt (p-Akt) and phosphorylated ERK (p-ERK) increased immediately after reperfusion, peaked at 4 hours (p-Akt) or 2 hours (p-ERK), decreased at 12 hours, and then increased at 24 hours. Phosphorylated JNK expression reduced after reperfusion, increased at 12 hours to near normal levels, and then showed a downward trend at 24 hours. Pearson linear correlation analysis also demonstrated that the number of apoptotic cells negatively correlated with p-Akt expression. These findings suggest that activation of Akt may be a key contributing factor in the delay of neuronal apoptosis after spinal cord ischemia, particularly at the stage of reperfusion, and thus may be a target for neuronal protection and reduction of neuronal apoptosis after spinal cord injury.

MiR-155 augments CD8+ T-cell antitumor activity in lymphoreplete hosts by enhancing responsiveness to homeostatic γc cytokines

Lymphodepleting regimens are used before adoptive immunotherapy to augment the antitumor efficacy of transferred T cells by removing endogenous homeostatic "cytokine sinks." These conditioning modalities, however, are often associated with severe toxicities. We found that microRNA-155 (miR-155) enabled tumor-specific CD8(+) T cells to mediate profound antitumor responses in lymphoreplete hosts that were not potentiated by immune-ablation. miR-155 enhanced T-cell responsiveness to limited amounts of homeostatic γc cytokines, resulting in delayed cellular contraction and sustained cytokine production. miR-155 restrained the expression of the inositol 5-phosphatase Ship1, an inhibitor of the serine-threonine protein kinase Akt, and multiple negative regulators of signal transducer and activator of transcription 5 (Stat5), including suppressor of cytokine signaling 1 (Socs1) and the protein tyrosine phosphatase Ptpn2. Expression of constitutively active Stat5a recapitulated the survival advantages conferred by miR-155, whereas constitutive Akt activation promoted sustained effector functions. Our results indicate that overexpression of miR-155 in tumor-specific T cells can be used to increase the effectiveness of adoptive immunotherapies in a cell-intrinsic manner without the need for life-threatening, lymphodepleting maneuvers.

Activation of AKT signaling promotes epithelial–mesenchymal transition and tumor growth in colorectal cancer cells

Activation of the serine-threonine protein kinase AKT has emerged as a central feature of epithelial-mesenchymal transition (EMT), which is the initial step for metastasis in many cancer models, including colorectal cancer. The focus of our study was to dissect the role of AKT and its molecular regulation of EMT in colorectal cancer. HCT-116 colorectal cancer cells stably overexpressing AKT (AKT/HCT-116) showed significantly higher cell proliferation compared with vector-transfected cells (pCMV/HCT-116). Elevated expression of important EMT-related transcription factors and genes such as Snail, Slug, β-catenin, vimentin, and MMP-9 correlated with increased migration and invasion by AKT/HCT-116 cells. Further, in vivo studies confirmed that AKT/HCT-116 xenografts were highly aggressive and angiogenic in nature compared with pCMV/HCT-116 xenografts. Molecular analysis of tumor samples revealed transcriptional regulation of Snail, Slug, β-catenin, MMP-2, and MMP-9 in AKT/HCT-116 tumors. These results were supported by immunohistochemistry analysis. Low levels of E-cadherin expression with a concomitant increase in and nuclear localization of β-catenin were evident in AKT/HCT-116 tumors compared with control tumors. Increased microvessel formation coincident with high expression of Factor VIII and increased numbers of reticulocytes confirmed the angiogenic property of AKT/HCT-116 tumors. Our results confirm the potential role of AKT signaling in regulating EMT and angiogenesis in colorectal cancer and suggest that inhibition of AKT can serve as an important therapeutic strategy in modulating EMT in colorectal cancer growth and metastasis.